Apparatus and method for growing crystals having a controlled internal junction structure



May 14, 1957 J. K. BELANG 2,791,813

. APPARATUS AND METHOD FOR GROWING CRYSTALS HAVING A CONTROLLED INTERNAL JUNCTION STRUCTURE Filed Oct. 28,' v1954 Ooooooo INVENTOR y JIAHS K. DELANO PL/ICED HERE ,4TH SPEC/FIC STR ra 41u25 47 STR TA ,4A/62E APPARATUS AND METHD FOR GRWING CRYSTALS HAVING A CONTROLLED IN- TERNAL JUNCTION STRUCTURE James K. Delano, Rye, N. Y.

Application October 28, 1954, Serial No. 465,20)

6 Claims. (Cl. 22-58) This invention relates to structure and method to predetermine the internal boundary or juncture definition of a growing crystal and more particularly to the structure of the vessel in which the crystal is grown, in order to create, in respect -to a major-growth axis thereof, symmetrically angled strata `or laminae, if the composition of the melt grows in arrays of strata or if the melt cornp'osition grows in clusters of discreet orientation, the practice 'of this invention forms at substantially precise planes within the growing crystal, junctures of differently angled growth of the crystal.

'These multiple junctures, thus formed, are most de` sirable for certain usages in the electrical arts, notably infpyro and thermo electric generation, and the like. The

angulated junctures of stratified growth or junctures formed by the differently orientated clusters induced by this invention, vwhen using such metallic solutions as those composed of bismuth, antimony and the like, produce multiple energy-junctures within the crystal body, formed in extending repetition along the extent of its growth.

It is to be noted then, that if a particular melt grows in strata formation that two predetermined growths of distinct inclination of strata, one to the other, on contacting in their growth as they enter the unitary or main portion of the crystal growing vessel, form a single repetitive juncture, normally bisecting the vertical axis f the vessel at their juncture faces. Three predetermined growth-sources, from respective radial seeding poin-ts, will produce three juncture faces, Iand so on, as the respective substantially radially disposed and predetermined seeding points or cornucopias are increased in number. Each resulting precise seed-growth issuing from its capillary-Cornucopia forms a segment in the main body of.` the' vessel of its own particular inclination of crystal growth in respect tothe other segments. In the c ase of a cluster-like growth this same angulated juncture-structure takes form along planes of substantially predetermined position within the crystal.

To properly utilize this invention and its novel `plural-` ity iof junctured strata or cluster contacting junctures the crystal, after being grown, is cut in sections, to make these junctures available for use in the electrical arts, the plane of each section so cut being substantially normal to the major axis of the crystals growth.

The juncture faces of the crystal may be formed according to the teaching of this invention, composed of a single metal or in combination of two or more distinct metals or` alloys of different composition.

jlt is well known that Messrs. Obreimov and Schubnikov, see Z. Physik 1924, as well as Professor Bridgman of Harvard University in the early twenties of this century devised and originated either a vessel, tapered at its end to'a'capillary point or formed with a length in the crystal growingv vesesl of a capillary section, the aim being to allow onlyone lone seed to survive therefrom yand toperpetuate its particular growth to form a uni-tary large' crystal.

This invention is an elaboration-of this theme to create a specific crystal structure having innumerable junctures formed by dissimilar angula-ted strata or orientated clus-v ters as and for the purposes set forth, whereas Messrs.

eratepredetermined disposed junctures along the con.

tacting faces of such strata or clusters.

2. The generation within 'the body of a growingcrystall of a plurality of junctures or ydissimilar inclinations formed in aplane substantially parallel with the taxis of growth, the subsequent sectionalizing of said crystalalong a plane normal to its axis of growth, the junctures in said cut sections defining a plurality of pole faces capable of generating opposite polarities when subjected to thermall gradients.

3. A crystal growing vessel or apparatus adapted to grow a crystal of the internal structure as described in object No. 1.

Further objects of my invention are implicit in the accompanying specifications and drawings, in which:

Figure 1 is a sectional elevation of the invention.

Figure 2 is a section taken along the line 2-2 in Figure 1.

Figure 3 is a section taken along the line 3--3 in Figure 1 without any crystal growing melt therein to show the interior contours of the vessel.

Figure 4 is a sectional view of the resulting crystal growth from a vessel as seen in Figure 1 and indicating Figure 7 is an elevation partially in section of a moditication of the invention to obtain predetermined junctures in a crystal body.

Referring to Figure 1, numeral 1 is the vessel in which` Numerals.

the crystal of specific. structure is. grown. 2 and 3 are the radially formed cornucopias with capillary seedings terminals 5 and 6 preferably formed as extending divisions of the base of vessel 1. These extend# ing divisions merge at 4 with vessel l, which is seen ini plan in Figure 3.

Around or in heating proximity to the extending di visions 5 and 6 of vessel 1 are positioned resistance coils 7 and 8 in series connection, one with the other, through lead wires 9 and 10 leading to electric supply terminals 40 and 41. A rheostat, 11, is interposed in lead wire 10.to control the heating effect from coils 2 and 3 in respect to seeding terminals 5 and 6 and the conically formed divisions 2 and 3. Likewise resistance coils 12, 14 and 16 are in similar heating relation with the main vessel 1 positioned one above the other, each of which being conl trolled as to their heating effect by rheostats 13, 15 and 17 respectively.

The operation of the crystal growing procedures of my invention is briey as follows:

Vessel 1 is lled with a specific melt as previously detned andthe several resistance coils viz.: 7 8, 12, 14 and 16 are energized to bring the melt to or slightly above its particular temperature necessary for a molten state. The

rheostat 11 is now manipulated to reduce the temperature at the initial seed growth capillaries at 5 and 6. Due to the series winding of coils 7 ,and 8, a cooling factor of Patented May 14, 1957 n 3 the same degree can be readily maintained at these divergent points, essential to a coincident starting of the seeding growth thereat. By a proper varying of the electrical energization of coils 12, 14 and ,16 by control of rheostats,

13 15 and 17 as the crystal growth progresses upwards` into the vessel 1, a proper gradient of Vtemperature is maintained inthe melt 21, care being taken to progressively lower the temperature of melt 21Y as and at the critical point at which the actual growth of crystallization is taking place as it grows up through the divided extensions 2.and 3 into the body of vessel 1. The rate of growth due to the heating and cooling means illustrated can be controlled so that thetwin growths are substantially equal as they progress through cornucopias 2 and 3 and contact each other andpass the apex-4 of the divisions in vessel 1 andthe -twogrowths-form the'juncture face 2% in extending array in vessel 1. The equal rate of growth of these two separate crystal growth-zones is very important to maintain juncture face 20 in vessel 1 at substantially in an axial midposition as is illustrated in Fig. 1 at numeral 20. Further describing and exemplifying the operation, as stated, various metals and alloys of different metals mayrbeused, in the lower melting class metals suchas antimony, bismuth, etc. For simplicity of describing the operation and the making of the joined nished bi-crystal I-willr select tin which is granulated and vessel 1 is lled through the central opening at the top, filling the extension arms 5, 6 and the central body about three-quarters full.

(hirrentl is now supplied to the heating coils 7, 8, 12, 14, 16 to heat vessel 1 and melt the contents and -hold the temperaturevslightly abovethe melting point. While in this lmolten state the vessel is shaken or vibrated which will cause any air or impurities to rise to the surface and allow .the metal to settle to the extreme ends of the arms, any dross or oxides that are on the upper or open end of the central chamber can remain without affecting the result.

This system of temperatureV gradient control symbolized by rheostats 11, 13, 15 and 17- must be necessarily indexed by a similar series of thermometers` (not` shown) extend-- ing in comparable elevations with the respective heating coils 7 8, 12,14 vand 16 along the extent of vessel 1. The requirements for melting and crystallizing of many metals at higher temperatures beyond which resistancetype -ofheating, is to be noted and as these requirements are knownand available for melting at higher temperatures, drawings and descriptions were omitted from the specification... Themethod of melting and controlled cooling as describedv for the resistance type is thesame for either type-f Ithas Abeenprovedby actual practice Athat ina conically formed capillaryv terminus of a vessel as above describiedand illustrated` at and 6 that there is a crowding out of other crystal seeds by the most favorably disposedl or situated seed and that the angulation of this precise surviving seed growth will persist even if the. configuration, or axis of the extending vessel in which the crystal growsforms a SiO-degree arc. The stratification or clusterorientation will not be altered as the crystal proceeds to grow therethrough.

In Figure 5 a modification of the unitary glass vessel 1 is shown, whereinvessel 1 is composed of two metallic ceramic halves` respectively, 22 and 23,. with extending anged portions 24 and 25 suitably secured, one to the other. The melt 21, when it has crystallized as previously explained, may be easily extracted in toto ,by the parting of; sections 22 and 23. Likewise the resistance coil as indicated by 25 to maintainthe necessary temperature gradient asit follows the crystal growth is sustained in ceramic insulation 2." held by supports Z8 and '29. It is evidentl tov those skilled in this art that these supports may achievable up or down along'the axis of vessell in ac cordancc with the desiredshifting Vtemperature gradient so essential to the equalized: crystal growth.`

1n.,Figure 6 is-shown in-plan and partially in; sectiona crystal growing vessel havingrfour distinct seeding` terminals viz.: 30, 31, 32 and 33, formed by the radially disposed arcuate members 30a, 31a, 32a and 33a, all of equal length, which together form the closure for the base of the circular main vessel, portion 42, shown in section. The respective coincident crystal growths initiated at capillary terminals 30, 31, 32 and 33 under identical temperature gradient control as heretofore described, produce four different angulated crystal growths due to the divergent radial positions of the members 30a, 31a, 32a and 33a. The -respective crystal growths extend under their equal rate of growth'until they arrive into the uni tary circular portion 42 of the vessel whereat they form junctured-segments as indicated by numerals 35, 36, 37 and 38, composed, if the melt forms a stratified growth of dilerently angulated faced junctures or if the melt forms into a series of clusters, create juncture faces of differently orientated crystal clusters.

Referring to Figure 7, this illustrates a modication of. the invention. Instead of relying on radially formed extending portions which terminate at capillary ends as seen at 5 and 6 in Figure l, to obtain a plurality of diierentially angulated strata or clusters of crystal orientations therefrom to produce the juncture faces 20 in repetitive array in vessel 1, the desired differential of strata or cluster orientation may be produced in members 43 and 44 by positioning a plural seeding of crystals, that is, a small fragment of crystal as seen at numerals 57 and 58, where in by a prior microscopic examination thereof, it has been ascertained that the inclination of the crystal seedingfragf ments are such and such and that the crystal fragmentsl have a cluster orientation or a strata formation. In this manner, by the proper placement of crystal seedings 57 and 58 opposite the open ended conicalcapillary openings 45 and 46 respectively, proper diierential inclinationcr orientation, one in respect to the other, can be obtained,A

resulting in the desired junctured-,growth In brief, the operation is as follows,Y and in substanceand grow to produce juncture 20 from the resultingdual' growths Y,as represented vby numerals118yand '19, similar to those junctures 2i). alreadyy described. It is noted that the crystal seeding fragments 57 and 58v are-physicaliy sustained and forced tight against the. capillary orifices-45 and 46 in Ythe conical tubular extensions 431 and 44 of vessel 42 by a` block 47 which, dueto its mass, acts asav chilling agent as well as a physical support for-seedings4 57 and 58, so that the temperature of -seedings 57 and58 is kept below their meltingpoint as when resistance coils 48, 49 and55 initially heat up to a molten state the melt 21 in vessel 42.

It is to be noted that the degree of laminations or strata indicated in Figures l, 4 and? by the numerals 18and 19 are purely illustrative andare Yshown only to indicate their approximate inclination oneto the other.

In Figure 4, the dot and dash lines 60 and Y61 are the cutting lines normal to the growth of the crystal through which a` section ofthe crystal is cut.A Whenwires 63and. 64 are secured ,to section 65, so` cut, and a thermal gradient is present, voltage is generated, as indicated.

Figs. l, 6, 7 may beusedyfor producingbicrystal see-- tions of distinctlydifferent metals and alloys.; ByA ern.-v ploying a diierentmetal. in the separate-arms and a ture of thetwoselectedmetals in the -tubefor center'section, the melt will on crystallizing cause the mixed metals--` tojoin its own type and-.set upa boundaryrlbetweenhthe two growths.A

What I desire to protect by U. S. Letters Patent is encompassed in the following claims.

I claim:

l. The method of growing in a vessel predetermined junctures in a crystal grown from a melt which consists in initiating substantially coincident but separated plural seed-growths of differential stratification in the melt thereof, continually promoting respective seed-growths therefrom by regulated heating to rise into a single compartment of said vessel at substantially equal growth rates whereby the crystal formed in said vessel is composed of component portions of said plurality of coincident but initially separate growths, thereby forming junctures at their respective contacting faces within said crystal.

2. The method of growing in a vessel predetermined junctures in a crystal grown from a melt which consists in initiating substantially coincident out separated plural seedings in the melt thereof from a plurality of radially conically formed terminations of said vessel, continually promoting respective surviving seed-growths therefrom by regulated heating to rise into a single compartment of said vessel from said terminations at substantially equal growth rates whereby the crystal formed in said vessel is composed of component portions of said plurality of coincident but initially separate growths, thereby forming junctures at their respective contacting faces.

3. An apparatus for growing crystals from a melt comprising a vessel, a plurality of depending substantially conical tubular portions forming in aggregate the closure of the base of said vessel, means to heat said vessel and said extending portions thereof and means to control said heating means and adapted to provide a gradient of temperature along the extent of said apparatus.

4. In a vessel of the character described, a substantially tubular section comprising one end of said vessel and a plurality of radially and downwardly disposed substantially conically shaped portions forming closures at the opposite end of said vessel, each of said radially disposed tubular portions communicating and opening into said substantially tubular end section.

5. In a vessel of the character described for growing crystals, a substantially tubular main body section forming the upper part of said vessel and a plurality of curved tubular portions of substantially conical shape communieating with the bottom of said main tubular body portion and with each other and each of said conical tubular portions being closed at its bottom or pointed end.

6. In a vessel of the character described, a substantially tubular section comprising one end of said vessel, a plurality of radially and downwardly disposed substantially conically shaped portions forming closures at the opposite end of said vessel, each of said radially disposed tubular portions communicating and opening into said substantially tubular end section, means to heat said vessel and said extending portions thereof, and means to control said heating means and adapted to provide a gradient of temperature along the extent of said apparatus.

References Cited in the tile of this patent UNITED STATES PATENTS 1,256,929 Schaller Feb. 19, 1918 1,733,752 Karnage Oct. 29, 1929 1,793,672 Bridgrnan Feb. 24, 1931 2,683,676 Little et al July 13, 1954 2,694,024 Bond et al. Nov. 9, 1954 OTHER REFERENCES Article by Chalmers, publ. in Proc. Royal Society of London, series A, vol. 162, pp. 1Z0-127, 1937. 

1. THE METHOD OF GROWING IN A VESSEL PREDETERMINED JUNCTURES IN A CRYSTAL GROWN FROM A MELT WHICH CONSISTS IN INITIATING SUBSTANTIALLY COINCIDENT BUT SEPARATED PLURAL SEED-GROWTHS OF DIFFERENTIAL STRATIFICATION IN THE MELT THEREOF, CONTINUALLY PROMOTING RESPECTIVE SEED-GROWTHS THEREFROM BY REGULATED HEATING TO RISE INTO A SINGLE COMPARTMENT OF SAID VESSEL AT SUBSTANTIALLY EQUAL GROWTH RATES 